Neptune Is Discovered | World History Project Sep 23 1846 Neptune Is Discovered Discovered on September 23, 1846, Neptune was the first planet found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led astronomers to deduce that its orbit was subject to gravitational perturbation by an unknown planet. Neptune was subsequently found within a degree of its predicted position, and its largest moon, Triton, was discovered shortly thereafter, though none of the planet's remaining 12 moons was located telescopically until the 20th century. Neptune has been visited by only one spacecraft, Voyager 2, which flew by the planet on August 25, 1989. Galileo's drawings show that he first observed Neptune on December 28, 1612, and again on January 27, 1613. On both occasions, Galileo mistook Neptune for a fixed star when it appeared very close—in conjunction—to Jupiter in the night sky, hence, he is not credited with Neptune's discovery.

In 1821, Alexis Bouvard published astronomical tables of the orbit of Neptune's neighbor Uranus. Subsequent observations revealed substantial deviations from the tables, leading Bouvard to hypothesize that an unknown body was perturbing the orbit through gravitational interaction. In 1843, John Couch Adams calculated the orbit of a hypothesized eighth planet that would account for Uranus's motion. In 1845–46, Urbain Le Verrier, independently of Adams, developed his own calculations but also experienced difficulties in stimulating any enthusiasm in his compatriots. In June, however, upon seeing Le Verrier's first published estimate of the planet's longitude and its similarity to Adams's estimate, Airy persuaded Cambridge Observatory director James Challis to search for the planet. Challis vainly scoured the sky throughout August and September. Meantime, Le Verrier by letter urged Berlin Observatory astronomer Johann Gottfried Galle to search with the observatory's refractor.

Heinrich d'Arrest, a student at the observatory, suggested to Galle that they could compare a recently drawn chart of the sky in the region of Le Verrier's predicted location with the current sky to seek the displacement characteristic of a planet, as opposed to a fixed star. The very evening of the day of receipt of Le Verrier's letter on September 23, 1846, Neptune was discovered within 1° of where Le Verrier had predicted it to be, and about 12° from Adams' prediction. Challis later realized that he had observed the planet twice in August, failing to identify it owing to his casual approach to the work. Triton: Neptune's Odd Moon Triton: Neptune's Odd Moon By Elizabeth Howell, Space.com Contributor | June 30, 2016 06:12pm ET MORE The crescent planet Neptune and its crescent moon Triton, as seen by NASA's Voyager 2 spacecraft in 1989. Credit: Voyager 2, NASA Triton is the largest of Neptune's moons.

Discovered in 1846 by British astronomer William Lassell – just weeks after Neptune itself was found – the moon showed some strange characteristics as astronomers learned more about it. To NASA's knowledge, Triton is the only moon in the solar system that orbits in a direction opposite to the rotation of its planet . Additionally, its surface is a study of contrasts, with smooth plains appearing to be right next to cratered surfaces. No spacecraft has gone to Neptune since the 1980s, but telescopes are capturing new data on Triton from the ground. A notable recent find was discovering seasons on the moon , using the European Southern Observatory's Very Large Telescope in Chile. Renewed interest in Triton began shortly after the New Horizons mission flew past Pluto in 2015. NASA released the best high-resolution map of Triton to date in 2014 in anticipation of the flyby, because it is believed that Triton and Pluto could share a similar history. They are of similar size, have nitrogen in their atmospheres and also icy surfaces. Discovery and flyby Triton was found on Oct. 10, 1846, just 17 days after Neptune was discovered.

According to NASA, Triton was known simply as " the satellite of Neptune " until 1949, when a second moon (Nereid) was found. All of Neptune's moons, according to International Astronomical Union guidelines, are named after Roman or Greek mythological characters associated with Neptune, Poseidon or oceans. Astronomers had to wait well over a century to see Triton as more than a dot, however. In 1977, NASA sent two Voyager probes on a one-way trip through the outer solar system, taking advantage of a rare planetary alignment that allowed them to move from one location to the next without using a lot of fuel. Voyager 2 flew by Neptune and its system on Aug. 25, 1989. Among the spacecraft's most stunning finds: icy volcanism is likely taking place on Triton's surface . Voyager 2 took pictures of "several geyser-like volcanic vents that were apparently spewing nitrogen gas laced with extremely fine, dark particles," NASA later wrote on a website. The agency estimates the particles go as high as five miles (eight kilometers) before flowing downwind and striking the surface.

It also appears that a large portion of the surface has melted. NASA said that is probably because Neptune captured Triton, causing tidal heating that could have left the satellite liquid for at least one billion years. New discoveries after Voyager 2 Although no spacecraft will go by Neptune's system in the near future, computer models and higher-resolution telescopes on Earth are providing new information about Triton's history and environment. (NASA has also released new pictures of Triton from Voyager 2 at least as late as 2009.) In 2006, a model published in Nature suggested Triton was originally a binary system that passed too close to Neptune . The planet then pulled Triton away from its companion, which is possible because one member of the system always moves slower than the other. Four years later, long-range infrared observations with the European Southern Observatory's Very Large Telescope revealed that the thin atmosphere of Triton changes with the seasons. At the time the VLT looked at the planet, it was summer in the southern hemisphere, where the sun's warmth thickened the atmosphere . This color photo of Neptune's largest moon Triton was obtained by NASA's Voyager 2 probe on Aug.

24, 1989, from 330,000 miles away. The resolution is about 6.2 miles, sufficient to begin to show topographic detail. Credit: NASA/JPL New models of Neptune could also provide insights on Triton, such as one released in 2015 that looks at the gas giant's magnetosphere. The magnetic field appears to be particularly pronounced on one side , according to Voyager 2 data and the model, and scientists next want to figure out how this field could interact with Triton. Other information about Triton's history could come from studying small bodies in the solar system, such as Comet 67P/Churyumov–Gerasimenko. The Rosetta spacecraft gathered data that showed molecular nitrogen on the comet's surface in 2015. From that information, scientists are trying to figure out where the nitrogen came from and how it compares to other bodies with nitrogen in the solar system, such as Triton and Pluto. Astrobiologists are also considering that Triton could have water under its icy surface.

"I think it is extremely likely that a subsurface ammonia-rich ocean exists in Triton," said the University of Maryland's Saswata Hier-Majumder in a 2012 Astrobiology Magazine article republished on SPACE.com. “[But] there are a number of uncertainties in our knowledge of Triton's interior and past, which makes it difficult to predict with absolute certainty." One example: because no one is quite sure of the size of Triton's rocky core, that creates difficulty with calculating the amount of heating produced by the decay of radioactive isotopes, also known as radiogenic heating. More heating would increase the size of the ocean. Editor's Recommendations The moon Triton - History, orbit, atmosphere, surface, structure, exploration The moon Triton Triton. © based on NASA images Triton is the largest of Neptune’s moons. Triton has a diameter of roughly 2,700 kilometers. It rotates and orbits Neptune every 5.9 Earth days. And it is the seventh largest moon in solar system. While Neptune has a dozen other moons, Triton’s mass is literally twenty times greater than the rest of the moons put together. Triton is about two thirds the size of Earth’s moon.

Triton is unique for being a large moon with a retrograde orbit and its exotic early history. History of Triton Triton may have originated in the Kuiper Belt, a region beyond Neptune filled with rocky bodies ranging from tiny asteroids to the Plutoids. The Plutoids include the dwarf planet Pluto and similarly sized objects like Sedna and Makemake. This theory is further supported by the melted and reformed surface of Triton, giving it a relatively smooth surface. This theory is also backed up by the fact that Pluto itself crosses Neptune’s orbit; this means that Triton could have been a similar dwarf planet that crossed Neptune’s orbit but was captured by its gravity. Triton was discovered in 1846. William Lassell discovered Triton almost three weeks after Neptune itself was discovered by German astronomers. Triton is named for a son of the Greek god Poseidon or Neptune. Triton's odd orbit Triton is unique for being a large moon with a retrograde orbit. © NASA Triton orbits Neptune every 141 hours. Triton also rotates once per orbit, so that the same side always faces Neptune.

Triton is unique because it is the only large moon that has a retrograde orbit, an orbit opposite of the planet’s rotation. There are many small moons that have retrograde orbits which are known to be captured asteroids, including Neptune’s moon Nereid. However, Triton is the only large moon with this trait. Because of Triton’s eccentric orbit, it is the only moon whose polar regions alternate in facing the sun. However, Triton is not the only large orbit with this habit. Uranus also rotates on its side, presenting rotating such that its North and South poles alternate facing the Sun. Impact of Neptune’s pull on Triton Triton has a faint atmosphere. The thin atmosphere contains traces of methane, but it is mostly nitrogen. Triton has volcanic activity in the form of geysers. Neptune exerts significant tidal forces on Neptune. This has slowed its orbit, pulling Triton closer to Neptune to its current location. Tidal forces also power the volcanic activity on Triton, though it spews nitrogen gases instead of molten rock like Jupiter’s Io. Triton‘s orbit is not stable.

The gravitational pull of Neptune on the moon’s orbit will eventually pull Triton into Neptune or cause it to break up. Surface of Triton Kuiper Belt. © NASA images Triton has very few craters but several large cracks. This may mean that it is geologically very young, that the surface is very young, or that Triton drifted far out in space away from other objects that could impact it. If Triton is a captured dwarf planet, the tidal forces that currently drive its volcanic activity could have melted and reformed the surface, giving it the relatively smooth surface we see today. It has been theorized that the tidal forces of Neptune on the moon could have kept its surface liquid for up to a billion years. Triton could have also impacted one of Neptune’s earlier moons, putting it in an irregular orbit and melting much of the surface. This theory would also account for Neptune‘s faint ring and the four small moons within Neptune’s ring. Triton is one of the coldest objects in the solar system. Its surface temperature has been recorded to be as low as -235°C or 34°° Kelvin. Other temperature measurements have found the temperature to average 38° Kelvin, which is just above absolute zero.

Absolute zero is the temperature at which even molecular hydrogen comes to rest and these temperatures were recorded during Neptune’s spring, which reached its summer solstice in 2000. Triton is so cold that nitrogen becomes a solid, raining down as frost on the night side of the moon. Only Pluto and other Kuiper objects are thought to be as cold. Triton’s surface would appear red to a casual observer. The methane ice on its surface has been converted to compounds called tholins. These red colored molecules are the result of hydrocarbons exposed to ultraviolet light. Inside Triton Neptune, Neptune Information, Facts, News, Photos -- National Geographic This requires the latest version of Flash Player. Click here to download. Invisible to the Naked Eye The eighth planet from the sun, Neptune was the first planet located through mathematical predictions rather than through regular observations of the sky.

(Galileo had recorded it as a fixed star during observations with his small telescope in 1612 and 1613.) When Uranus didn't travel exactly as astronomers expected it to, a French mathematician, Urbain Joseph Le Verrier, proposed the position and mass of another as yet unknown planet that could cause the observed changes to Uranus's orbit. After being ignored by French astronomers, Le Verrier sent his predictions to Johann Gottfried Galle at the Berlin Observatory, who found Neptune on his first night of searching in 1846. Seventeen days later, its largest moon, Triton, was also discovered. Nearly 2.8 billion miles (4.5 billion kilometers) from the sun, Neptune orbits the sun once every 165 years. It is invisible to the naked eye because of its extreme distance from Earth. The main axis of Neptune's magnetic field is "tipped over" by about 47 degrees compared with the planet's rotation axis. Like Uranus, whose magnetic axis is tilted about 60 degrees from the axis of rotation, Neptune's magnetosphere undergoes wild variations during each rotation because of this misalignment.

The magnetic field of Neptune is about 27 times more powerful than that of Earth. Neptune's atmosphere extends to great depths, gradually merging into water and other "melted ices" over a heavier, approximately Earth-size solid core. Neptune's blue color is the result of methane in the atmosphere. Uranus's blue-green color is also the result of atmospheric methane, but Neptune is a more vivid, brighter blue, so there must be an unknown component that causes the more intense color that we see. The cause of Neptune's bluish tinge remains a mystery. Mystery Storm Despite its great distance from the sun and lower energy input, Neptune's winds are three times stronger than Jupiter's and nine times stronger than Earth's. In 1989, Voyager 2 tracked a large, oval, dark storm in Neptune's southern hemisphere. This hurricane-like Great Dark Spot was observed to be large enough to contain the entire Earth. It spun counterclockwise and moved westward at almost 750 miles (1,200 kilometers) per hour. (Subsequent images from the Hubble Space Telescope showed no sign of the Great Dark Spot photographed by Voyager.

A comparable spot appeared in 1994 in Neptune's northern hemisphere but had disappeared by 1997.) Voyager 2 also photographed clouds casting shadows on a lower cloud deck, enabling scientists to visually measure the altitude differences between the upper and lower cloud decks. The planet has six rings of varying thicknesses, confirmed by Voyager 2's observations in 1989. Neptune's rings are believed to be relatively young and relatively short-lived. Neptune has 13 known moons, six of which were discovered by Voyager 2. The largest, Triton, orbits Neptune in a direction opposite to the direction of the planet's rotation. Triton is the coldest body yet visited in our solar system—temperatures on its surface are about -391 degrees Fahrenheit (-235 degrees Celsius). Despite this deep freeze, Voyager 2 discovered geysers spewing icy material upward more than five miles (eight kilometers). Triton's thin atmosphere, also discovered by Voyager, has been seen from Earth several times since, and is growing warmer—although scientists do not yet know why.

—Text courtesy NASA/JPL Neptune's Moon Triton Triton From The Hubble Space Telescope This image of Triton was taken by the Hubble Space Telescope's Faint Object Camera in September of 1995. It was created from a blue and ultraviolet image. The color is false but closely matches the color observed from voyager images. Triton appears to be roughly 10% darker than in images taken by the Voyager 2 spacecraft. Also note that the equatorial region is bright, but there is a darker region around the pole. With Triton's long seasons, the southern summer has been progressing, and the south pole has received increasing sunlight; thus, it is probable that much of the frost covering the region in 1989 has evaporated, some of which may have condensed at the equator (hence the bright region there). This image truly pushes the limit of HST's resolving power. The image is centered at roughly 215 degrees latitude. (Courtesy of Ted Stryk) South Pole of Triton This high resolution image of Triton was obtained by Voyager 2 on August 25, 1989. It shows the moon's south polar cap.

One of the unusual aspect of this image is the dark streaks in the images. Perhaps they were made by geyser-like eruptions of nitrogen. The geyser eruptions could have carried darker materials from the crust. The light regions probably consist of layers of nitrogen. (Credit: Calvin J. Hamilton) Triton in 3D This is a computer-generated perspective rendering of one of the caldera -like depressions on Triton, as it would appear if viewed from the northeast. The image was obtained Aug. 24, 1989, when the Voyager spacecraft was about 181,800 kilometers (112,900 miles) from Triton. The caldera floor shown in this image is approximately 200 kilometers (120 miles) in diameter. It is extremely flat and probably was formed by the volcanic eruption of ice lavas of very low viscosity. The bench visible in the foreground may be a remnant of earlier flooding to a level about 200 meters (600 feet) higher than the present caldera floor.

(Courtesy NASA/JPL) Surface of Triton This is one of the most detailed views of the surface of Triton taken by Voyager 2 on its flyby of the large satellite of Neptune early in the morning of August 25, 1989. The picture was taken from a distance of 40,000 kilometers (25,000 miles), the frame is about 220 kilometers (140 miles) across and shows details as small as 750 meters (0.5 miles). Most of the area is covered by a peculiar landscape of roughly circular depressions separated by rugged ridges. This type of terrain, which covers large tracts of Triton's northern hemisphere, is unlike anything seen elsewhere in the solar system. The depressions are probably not impact craters: They are too similar in size and too regularly spaced. Their origin is still unknown, but may involve local melting and collapse of the icy surface. A conspicuous set of grooves and ridges cuts across the landscape, indicating fracturing and deformation of Triton's surface. The rarity of impact craters suggests a young surface by solarsystem standards, probably less than a few billion years old.

(Courtesy NASA/JPL) Dark Areas on Triton Voyager 2 acquired this black and white image of Triton during the night of August 24-25, 1989. Triton's limb cuts obliquely across the middle of the image. The field of view is about 1,000 km (600 miles) across. Three irregular dark areas, surrounded by brighter material, dominate the image. Low-lying material with intermediate albedo occupies the central area, and fresh craters occur along the right margin. Sub-parallel alignment of linear patches of dark material shown in the lower and left part of the image suggests that the patches are structurally controlled. (Courtesy NASA/JPL) Post Encounter Images of Triton This set of images shows the best views of Neptune's moon Triton taken by Voyager 2 as the spacecraft withdrew from the Neptune system on August 25, 1989. The top four images were constructed from various color image bands as Voyager receded from Triton. (Courtesy Ted Stryk) Montage of Neptune and Triton This computer generated montage shows Neptune as it would appear from a spacecraft approaching Triton.

The wind- and sublimation-eroded south polar cap of Triton is shown at the bottom of the Triton image, a cryovolcanic terrain at the upper right, and the enigmatic cantaloupe terrain at the upper left. Triton's surface is mostly covered by nitrogen frost mixed with traces of condensed methane, carbon dioxide, and carbon monoxide. The tenuous atmosphere of Triton, though only about one-hundredth of one percent of Earth's atmospheric density at the surface, is thick enough to produce wind-deposited streaks of dark and bright materials of unknown composition in the south polar cap region. The southern polar cap was sublimating at the time of the Voyager 2 flyby, as indicated by the irregular and eroded appearance of the edge of the cap. The polar frosts were sublimating because Triton's orbital and rotational motion causes the sun to shine directly on the polar cap for a period of several decades during Neptune's and Triton's long austral summer. Though the polar cap was undergoing heat death, surface temperatures still were only about 38 K (-391 degrees Farenheit).

(Courtesy NASA/JPL) Neptune on Triton's Horizon Composite view showing Neptune on Triton's horizon. Neptune's south pole is to the left; clearly visible in the planets' southern hemisphere is a Great Dark Spot, a large anticyclonic storm system located about 20 degrees South. The foreground is a computer generated view of Triton's maria as they would appear from a point approximately 45 km above the surface. The terraces visible in this image indicate multiple episodes of 'cryovolcanic' flooding. This three-dimensional view was created from a Voyager image by using a two-dimensional photoclinometric model. Relief has been exaggerated roughly 30-fold, the actual range of the relief is about 1 km. Would Neptune appear to be rising or setting? Neither, due to the motion of Triton relative to Neptune, it would appear to move laterally along the horizon, eventually rising and setting at high latitudes. (Courtesy NASA/JPL) Who Discovered Triton the Largest Moon of Neptune? Interesting Facts About Neptune’s Moon Triton Who Discovered Triton?

written by: Anurag Ghosh•edited by: George Adcock •updated: 2/19/2010 It was the British astronomer William Lassell who discovered Triton, the largest moon of Neptune on October 10, 1846, a month after Neptune’s discovery. The name “Triton" was first put forward by French astronomer Nicolas Camille Flammarion in 1880. slide 1 of 4 Neptune--Born in Controversy Aptly named after the Roman god of the sea, the enchanting blue-hued planet is the fourth largest in our solar system. Neptune was first observed by Galileo Galilee on December 28, 1612, but it was thought to be a fixed star. During 1821-46, two brilliant minds—Urbain Le Verrier and John Couch Adams—began their quest to search for Neptune and conducted independent mathematical calculations to locate this planet. Much controversy occurred between the supporters the French mathematician and British astronomer and mathematician over the initial accurate discovery of the planet Neptune. However, the controversy ceased as both Adams and Le Verrier were together declared discoverers.

Besides controversies, Neptune is also known for its moons—13 of them. Of the 13 moons, the largest moon is Triton, which is best known for its retrograde orbit. But, who discovered Triton the largest moon of Neptune? Was there another controversy on this discovery? Let’s see. slide 2 of 4 Who Discovered Triton? A month after Neptune was discovered by German astronomers Johann Gottfried Galle and Heinrich Louis d’Arrest, Neptune’s moon Triton (pronounced Try-tun), caught the eye of British astronomer William Lassell on October 10, 1846. By profession, Lassell was an expert brewer but also had a deep interest in astronomy. He began constructing his own telescope in 1820. After the discovery of Neptune, Lassell received a letter from John Herschel suggesting a search for Neptune’s moons. Neptune was discovered by German astronomers on September 23, 1846 and within 17 days, Lassell discovered Triton, Neptune’s largest moon. Neptune’s moon Triton is named after Poseidon’s son—the Greek equivalent of the Roman God Neptune.

Almost all discovered moons of Neptune are named after the characters from Greek and Roman mythology. The name “Triton" was first proposed in 1880 by French astronomer and author Nicolas Camille Flammarion in his book Astronomie Populaire. However, the name was not adopted for several decades. Quite interestingly, Triton was simply known as the “satellite of Neptune" until 1949, when the second moon Nereid was discovered by Gerard P. Kuiper. In a nutshell, it was the British astronomer William Lassell who discovered Triton the largest moon of Neptune in 1846 and the name “Triton" was first suggested by French astronomer Nicolas Flammarion in 1880. slide 3 of 4 Interesting Facts About Triton Triton is the only largest moon that orbits in the direction opposite to the movement of the planet. This phenomenon is called retrograde orbit. The physical characteristics of Triton are very similar to Pluto. For that reason scientists presume that Triton was also a Kuiper Belt Object , which was captured by Neptune’s gravity a million years ago. The main gases that compose Triton’s thin atmosphere include nitrogen and methane.

Also, Triton is one of the most volcanically active bodies in our solar system. Neptune’s moon Triton is also one of the coolest entities in the solar system. NASA’s Voyager 2 was the first spacecraft to observe Triton and Neptune. It began analyzing the moon during its 1989 flyby. Voyager 2 found the surface temperature of Triton to be -391 degree Fahrenheit. It observed that Triton is one of the few moons in the solar system to have active geysers . slide 4 of 4 “Triton Information and Facts" Neptune’s Moon Triton “Triton" Wikipedia 1. Triton Mosaic Image: 2. Photograph of William Lassell: 3. Color Image of Neptune’s Moon Triton: ◄ ● ● ● ● ► Triton Moon | PlanetsEdu.com Triton Triton Triton is one of Neptune’s moons. It was discovered in 1846 by the British astronomer William Lassell.

Diameter: 2.71 x 106 m Mass: 2.14 x 1022 kg Composition: Nitrogen, water-ice, methane, carbon dioxide Orbit: 3.54 x 106 m from Neptune Triton is the largest of Neptune’s moons and the 7th largest moon in the Solar System. Neptune has 13 known moons. 6 are regular satellites with orbits in the same direction as the spin of the planet and there are 7 that orbit in the opposite direction to the planet’s spin. Neptune’s moons take their name from Roman and Greek water gods because of Neptune’s (Poseidon’s) position as the god of the sea. Triton was the son of Poseidon and the messenger of the ocean. The name was first proposed by French astronomer Nicholas Camille Flammarion, though it was not adopted by the International Astronomical Union (IAU) until the 1950s. Triton is composed of a frozen nitrogen crust and an interior of water-ice, carbon-dioxide ice and some frozen methane and carbon monoxide. There may be surface ammonia and ammonia hydrates.

The moon is coloured red as a result of tholins. These are organic compounds created by the ultraviolet irradiation of ethane and methane. There may be a small rocky core and a liquid water layer in the interior. Heat from the radioactive decay of the rock may cause convection currents within Triton’s mantle. Triton has a relatively flat surface, though there are features such as ridges, furrows, plateaus, plains and a few craters. Heights are usually less than one kilometre. The moon is geologically active. Some complex valleys and ridges could be the result of cryovolcanism – an extrusion of water-ice and ammonia rather than molten rock. There are a few eruptions of dust and nitrogen in plumes that reach heights of 8 km. There are reflective frozen nitrogen and methane caps on the polar region that are marked with impact craters. The oldest terrain on Triton resembles the skin of a cantaloupe melon and is called “cantaloupe terrain”. This is mostly dirty water-ice with depressions of about 30 to 40 km in diameter.

Triton’s atmosphere consists of nitrogen with additional traces of methane and carbon monoxide close to the surface. Turbulence on the surface of the moon creates weather conditions in its troposphere. There are no other higher atmospheric layers, such as the stratosphere on Earth that protects Earth from solar radiation. Consequently, a haze of hydrocarbons and nitriles – compounds of carbon and nitrogen such as cyanides – permeates through Triton’s troposphere. Triton has a retrograde orbit, meaning that it orbits in the opposite direction to Neptune’s spin. This implies that Triton was a captured object that originated in the Kuiper Belt, the region of outer space beyond Neptune. The orbit is synchronous, meaning that the moon itself spins on its own axis in the same direction as its orbital movement. Triton always keeps the same hemisphere facing Neptune. It takes 5.87 Earth days to orbit Neptune. Along with Neptune and its other satellites, Triton takes 164.79 Earth years to orbit the sun. The only spacecraft flyby of Triton was Voyager 2 in 1989. Its closest approach to Triton was 37,790 km. Share this with the Universe!

Triton Gallery BBC - Solar System - Triton (pictures, video, facts & news) Saturn, Neptune and Triton's future It is predicted that Saturn will lose its rings. In one hundred million years it is predicted that Saturn's rings will disappear. In one billion years, Neptune may develop its own rings when its moon Triton spirals from orbit and disintegrates into countless fragments. About Triton Triton is the largest natural satellite of the planet Neptune. It was discovered on October 10, 1846, by English astronomer William Lassell. It is the only large moon in the Solar System with a retrograde orbit, an orbit in the opposite direction to its planet's rotation. At 2,700 kilometres (1,700 mi) in diameter, it is the seventh-largest moon in the Solar System. Because of its retrograde orbit and composition similar to Pluto's, Triton is thought to have been a dwarf planet captured from the Kuiper belt. Triton has a surface of mostly frozen nitrogen, a mostly water-ice crust, an icy mantle and a substantial core of rock and metal. The core makes up two-thirds of its total mass.

Triton has a mean density of 2.061 g/cm3 and is composed of approximately 15–35% water ice. Triton is one of the few moons in the Solar System known to be geologically active. As a consequence, its surface is relatively young with sparse impact craters, and a complex geological history revealed in intricate cryovolcanic and tectonic terrains. Part of its surface has geysers erupting sublimated nitrogen gas, contributing to a tenuous nitrogen atmosphere less than 1/70,000 the pressure of Earth's atmosphere at sea level. Neptune's Moon Triton - Universe Today Universe Today by Matt Williams The planets of the outer Solar System are known for being strange, as are their many moons. This is especially true of Triton, Neptune’s largest moon. In addition to being the seventh-largest moon in the Solar System, it is also the only major moon that has a retrograde orbit – i.e. it revolves in the direction opposite to the planet’s rotation. This suggests that Triton did not form in orbit around Neptune, but is a cosmic visitor that passed by one day and decided to stay.

And like most moons in the outer Solar System, Triton is believed to be composed of an icy surface and a rocky core. But unlike most Solar moons, Triton is one of the few that is known to be geologically active. This results in cryovolcanism , where geysers periodically break through the crust and turn the surface Triton into what is sure to be a psychedelic experience! Discovery and Naming: Triton was discovered by British astronomer William Lassell on October 10th, 1846, just 17 days after the discovery of Neptune by German astronomer Johann Gottfried Galle. After learning about the discovery, John Herschel – the son of famed English astronomer William Herschel, who discovered many of Saturn’s and Uranus’ moons – wrote to Lassell and recommended he observe Neptune to see if it had any moons as well. New Horizons image of Neptune and its largest moon, Triton, taken by the LORRI instrument on June 23, 2010. Credit: NASA Lassell did so and discovered Neptune’s largest moon eight days later.

Thirty-four years later, French astronomer Camille Flammarion named the moon Triton – after the Greek sea god and son of Poseidon (the equivalent of the Roman god Neptune) – in his 1880 book Astronomie Populaire . It would be several decades before the name caught on however. Until the discovery of the second moon Nereid in 1949, Triton was commonly known simply as “the satellite of Neptune”. Size, Mass and Orbit: At 2.14 × 1022 kg, and with a diameter of approx. 2,700 kilometers (1,680 miles) km, Triton is the largest moon in the Neptunian system – comprising more than 99.5% of all the mass known to orbit the planet. In addition to being the seventh-largest moon in the Solar System, it is also more massive than all known moons in the Solar System smaller than itself combined. With no axial tilt and an eccentricity of virtually zero, the moon orbits Neptune at a distance of 354,760 km (220,438 miles).

At this distance, Triton is the farthest satellite of Neptune, and orbits the planet every 5.87685 Earth days. Unlike other moons of its size, Triton has a retrograde orbit around its host planet. Most of the outer irregular moons of Jupiter and Saturn have retrograde orbits, as do some of Uranus’s outer moons . However, these moons are all much more distant from their primaries, and are rather small in comparison. Triton also has a synchronous orbit with Neptune, which means it keeps one face aimed towards the planet at all times. As Neptune orbits the Sun, Triton’s polar regions take turns facing the Sun, resulting in seasonal changes as one pole, then the other, moves into the sunlight. Such changes were observed in April of 2010 by astronomers using the European Southern Observatory’s Very Large Telescope . Another all-important aspect of Triton’s orbit is that it is decaying. Scientists estimate that in approximately 3.6 billion years, it will pass below Neptune’s Roche limit and will be torn apart. Composition: Triton has a radius, density (2.061 g/cm3), temperature and chemical composition similar to thatof Pluto.

Because of this, and the fact that it circles Neptune in a retrograde orbit, astronomers believe that the moon originated in the Kuiper Belt and later became trapped by Neptune’s gravity. Another theory has it that Triton was once a dwarf planet with a companion. In this scenario, Neptune captured Triton and flung its companion away when the giant gas moved further out into the solar system, billions of years ago. Also like Pluto, 55% of Triton’s surface is covered with frozen nitrogen, with water ice comprising 15–35% and dry ice (aka. frozen carbon dioxide) forming the remaining 10–20%. Trace amounts of methane and carbon monoxide ice are believed to exist there as well, as are small amounts of ammonia (in the form of ammonia dihydrate in the lithosphere). Triton’s density suggests that its interior is differentiated between a solid core made of rocky material and metals, a mantle composed of ice, and a crust. There is enough rock in Triton’s interior for radioactive decay to power convection in the mantle, which may even be sufficient to maintain a subterranean ocean.

As with Jupiter’s moon of Europa, the proposed existence of this warm-water ocean could mean the presence of life beneath the icy crusts. Atmosphere and Surface Features: Triton has a considerably high albedo, reflecting 60–95% of the sunlight that reaches it. The surface is also quite young, which is an indication of the possible existence of an interior ocean and geological activity. The moon has a reddish tint, which is probably the result of the methane ice turning to carbon due to exposure to ultraviolet radiation. Triton is considered to be one of the coldest places in the Solar System. The moon’s surface temperature is approx. -235°C while Pluto averages about -229°C. Scientists say that Pluto may drop as low as -240°C at the furthest point from the Sun in its orbit, but it also gets much warmer closer to the Sun, giving it a higher overall temperature average. It is also one of the few moons in the Solar System that is geologically active, which means that its surface is relatively young due to resurfacing. This activity also results in cryovolcanism, where water ammonia and nitrogen gas burst forth from the surface instead of liquid rock.

These nitrogen geysers can send plumes of liquid nitrogen 8 km above the surface of the moon. Triton (lower left) compared to the Moon (upper left) and Earth (right), to scale. Credit: NASA/JPL/USGS Because of the geological activity constantly renewing the moon’s surface, there are very few impact craters on Triton. Like Pluto, Triton has an atmosphere that is thought to have resulted from the evaporation of ices from its surface. Like its surface ices, Triton’s tenuous atmosphere is made up of nitrogen with trace amounts of carbon monoxide and small amounts of methane near the surface. This atmosphere consists of a troposphere rising to an altitude of 8km, where it then gives way to a thermosphere that reaches out to 950 km from the surface. The temperature of Triton’s upper atmosphere, at 95-100 K (ca.-175 °C/-283 °F) is higher than that at the surface, due to the influence of solar radiation and Neptune’s magnetosphere.

A haze permeates most of Triton’s troposphere, thought to be composed largely of hydrocarbons and nitriles created by the action of sunlight on methane. Triton’s atmosphere also has clouds of condensed nitrogen that lie between 1 and 3 km from the surface. Observations taken from Earth and by the Voyager 2 spacecraft have shown that Triton experiences a warm summer season every few hundred years. This could be the result of a periodic change in the planet’s albedo (i.e. its gets darker and redder) which could be caused by either frost patterns or geological activity. Using the CRIRES instrument on ESO’s Very Large Telescope, a team of astronomers has been able to see that the summer is in full swing in Triton’s southern hemisphere. Credit: ESO This change would allow more heat to be absorbed, followed by an increase in sublimation and atmospheric pressure. Data collected between 1987 and 1999 indicated that Triton was approaching one of these warm summers.

Exploration: When NASA’s Voyager 2 made a flyby of Neptune in August of 1989, the mission controllers also decided to conduct a flyby of Triton – similar to Voyager 1 ‘s encounter with Saturn and Titan. When it made its flyby, most of the northern hemisphere was in darkness and unseen by Voyager. Because of the speed of Voyager’s visit and the slow rotation of Triton, only one hemisphere was seen clearly at close distance. The rest of the surface was either in darkness or seen as blurry markings. Nevertheless, the Voyager 2 spacecraft managed to capture several images of the moon and spotted geysers of liquid nitrogen blasting out of two distinct features on the surface. In August of 2014, in anticipation of New Horizons impending encounter with Pluto, NASA restored these photos and used them to create the first global color map of Triton . Produced by Paul Schenk, a scientist at the Lunar and Planetary Institute in Houston, the map was also used to make a movie (shown below) that recreated the historic Voyager 2 encounter in time for the 25th anniversary of the event. Yes, Triton is indeed an unusual moon.

Aside from its rather unique characteristics (retrograde motion, geological activity) the moon’s landscape is likely to be an amazing sight. For anyone standing on the surface, surrounded by colorful ices, plumes of nitrogen and ammonia, a nitrogen haze and Neptune’s big blue disc hanging on the sky, the experience would seem like something akin to a hallucination. In the end, it is too bad that the Solar System will one day be saying good-bye to this moon. Because of the nature of its orbit, the moon will eventually fall into Neptune’s gravity well and break up. At which point, Neptune will have a huge ring like Saturn, until those particles crash into the planet as well. That too would be something to behold. One can only hope that humanity will still be around in 3.6 billion years to witness it! Here’s one about the New Map of Triton , and one about the Underground Ocean it might be hiding, and 40 Years of Summer on Triton . And here’s Why You Shouldn’t Buy Real Estate on Triton .

In the Observatory also has an interview with Emily Lakdawalla, the senior editor and planetary evangelist for the Planetary Society, titled “ Where Should We Look for Life in the Solar System? ” Sources:

Question: Which planet, whose largest moon is Triton, was discovered in 1846?
Answer: Neptune